Oxygen bleaching agents have become increasingly popular in recent years in household and personal care products to facilitate stain and soil removal. Bleaches are particularly desirable for their stain-removing, dingy fabric cleanup, whitening and sanitization properties. Oxygen bleaching agents have found particular acceptance in laundry products such as detergents, in automatic dishwashing products and in hard surface cleansers. Oxygen bleaching agents, however, are somewhat limited in their effectiveness. Some frequently encountered disadvantages include their lack of fabric color safety and their tendency to be extremely temperature rate dependent. Thus, the colder the solution in which they are employed, the less effective the bleaching action. Temperatures in excess of 60° C. are typically required for effectiveness of an oxygen bleaching agent in solution.
To solve the aforementioned temperature rate dependency, a class of compounds known as “bleach activators” has been developed. Bleach activators, typically perhydrolyzable acyl compounds having a leaving group such as oxybenzenesulfonate, react with the active oxygen group, typically hydrogen peroxide or its anion, to form a more effective peroxyacid oxidant. It is the peroxyacid compound which then oxidizes the stained or soiled substrate material. However, bleach activators are also somewhat temperature dependent. Bleach activators are more effective at warm water temperatures of from about 40° C. to about 60° C. In water temperatures of less than about 40° C., the peroxyacid compound loses some of its bleaching effectiveness.
Unsuccessful attempts have been made, as disclosed in U.S. Pat. Nos. 5,360,568, 5,360,569 and 5,370,826 all to Madison et al., to develop a bleach system comprising organic catalysts, more specifically, iminium-based organic catalysts, which is effective in lower temperature water conditions and is safe on colors. However, cationic, quaternary imine salts, the organic catalysts disclosed in these applications, are not completely satisfactory in laundry bleaching applications. In particular, the quaternary imine salts, when combined with peroxygen compounds, cause an unacceptable level of color damage on fabrics. In addition, the quaternary imine salts are less stable at higher wash temperatures, which can result in a loss of effectiveness.
U.S. Pat. Nos. 5,576,282 and 5,817,614 both to Miracle et al. disclose another attempt at developing a bleach system comprising organic catalysts which is effective in lower temperature water conditions and is safe on colors. Although the bleach system disclosed in this patent provides enhanced color-safety over traditional organic catalyst bleach systems at lower temperature water conditions, it is also preferred to achieve such bleaching also at higher wash temperatures.
Many iminiums and dihydroisoquinoliniums, and the quaternary oxaziridinium bleaching species formed from them, exemplified in the art have organic catalyst lifetimes of less than 30 min at 20° C., as determined according to the Test Protocol, disclosed hereinafter. At higher temperatures, such as 40° C., these organic catalyst lifetimes would be less than 3 min. At even higher wash temperatures, such as 60° C., the organic catalyst lifetimes would be less than 20 seconds. Such instability at warmer wash temperatures, can result in a dramatic loss of effectiveness.
In light of the foregoing, researchers have been pursuing effective organic catalyst bleach systems which provide effective bleaching both in lower (cold) and higher (warm or hot) water temperatures, and provide improved stability toward unwanted organic catalyst decomposition.
Accordingly, it is evident that there still exists a need for an organic catalyst bleach system that provides improved stability toward unwanted organic catalyst decomposition and that provides effective bleaching not only in lower temperature water conditions, but also more effective bleaching at higher temperature water conditions compared to the bleach systems disclosed in the prior art.